Package: util-linux
Version: 2.33.1-0.1
Severity: normal
Dear Maintainer,
* What led up to the situation?
I tried using unshare and nsenter with the pid (and mount) persistent
namespaces.
So I created new namespaces using unshare and tried to enter them using nsenter.
* What exactly did you do (or not do) that was effective (or
ineffective)?
Providing nsenter with the same persistent PID namespace file did not result in
entering the same PID namespace.
console #1
~ # mount --make-private /
~ # touch /tmp/test-{pid,mnt}
~ # unshare --pid=/tmp/test-pid --mount=/tmp/test-mnt --fork --mount-proc
~ # ps faxu
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 1.0 0.0 9652 4876 pts/7 S 23:22 0:00 -bash
root 8 0.0 0.0 12156 3144 pts/7 R+ 23:22 0:00 ps faxu
~ # mount
[all host mounts repeated here]
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
~ #
* What was the outcome of this action?
console #2 (with console #1 still open)
~ # nsenter --mount=/tmp/test-mnt --pid=/tmp/test-pid
/ # ps faxu
Error, do this: mount -t proc proc /proc
/ # mount
mount: failed to read mtab: Datei oder Verzeichnis nicht gefunden
console #3 (with console #1 + #2 still open)
~ # lsns --output-all -u
NS TYPE PATH NPROCS PID PPID COMMAND
UID USER
NETNSID NSFS
4026531835 cgroup /proc/1/ns/cgroup 420 1 0 /sbin/init noibrs
noibpb nopti nospectre_v2 nospec_store_bypass_disable no_stf_barrier 0 root
4026531836 pid /proc/1/ns/pid 419 1 0 /sbin/init noibrs
noibpb nopti nospectre_v2 nospec_store_bypass_disable no_stf_barrier 0 root
/tmp/test-pid
4026531837 user /proc/1/ns/user 420 1 0 /sbin/init noibrs
noibpb nopti nospectre_v2 nospec_store_bypass_disable no_stf_barrier 0 root
4026531838 uts /proc/1/ns/uts 420 1 0 /sbin/init noibrs
noibpb nopti nospectre_v2 nospec_store_bypass_disable no_stf_barrier 0 root
4026531839 ipc /proc/1/ns/ipc 420 1 0 /sbin/init noibrs
noibpb nopti nospectre_v2 nospec_store_bypass_disable no_stf_barrier 0 root
4026531840 mnt /proc/1/ns/mnt 395 1 0 /sbin/init noibrs
noibpb nopti nospectre_v2 nospec_store_bypass_disable no_stf_barrier 0 root
4026531860 mnt /proc/50/ns/mnt 1 50 2 kdevtmpfs
0 root
4026532000 net /proc/1/ns/net 420 1 0 /sbin/init noibrs
noibpb nopti nospectre_v2 nospec_store_bypass_disable no_stf_barrier 0 root
unassigned
4026532199 mnt /proc/436/ns/mnt 1 436 1
/lib/systemd/systemd-udevd
0 root
4026532209 mnt /proc/718/ns/mnt 1 718 1 /usr/sbin/irqbalance
--foreground 0 root
4026532361 mnt /proc/17407/ns/mnt 4 17407 15596 unshare
--pid=/tmp/test-pid --mount=/tmp/test-mnt --fork --mount-proc
0 root /tmp/test-mnt
4026532362 pid /proc/17409/ns/pid 1 17409 17407 -bash
0 root
~ # ps faxu
[excerpt]
root 17407 0.0 0.0 6772 756 pts/7 S 23:22 0:00 |
\_ unshare --pid=/tmp/test-pid --mount=/tmp/test-mnt --fork --mount-proc
root 17409 0.0 0.0 9652 4876 pts/7 S+ 23:22 0:00 |
\_ -bash
* What outcome did you expect instead?
I expected nsenter to join the pid namespace given.
I expected /tmp/test-pid to not shared PID namespace with /init but instead
with PID 17409.
This is probably due to the PID namespace not affecting the unshare main
process after the unshare syscall, but only its child processes.
Therefore bind_ns_files_from_child should probably call bind_ns_files not with
the parent (unshare process) process id but its child process id.
To fix it, instead of ns/pid, ns/pid_for_children could be used. Though,
ns/pid_for_children is empty before the first child has been created, so
unshare.c needs some more work than just replacing ns/pid with
ns/pid_for_children.
-- System Information:
Debian Release: 10.1
APT prefers stable
APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 4.19.0-6-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL
set to de_DE.utf8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set
to de_DE.utf8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages util-linux depends on:
ii fdisk 2.33.1-0.1
ii libaudit1 1:2.8.4-3
ii libblkid1 2.33.1-0.1
ii libc6 2.28-10
ii libcap-ng0 0.7.9-2
ii libmount1 2.33.1-0.1
ii libpam0g 1.3.1-5
ii libselinux1 2.8-1+b1
ii libsmartcols1 2.33.1-0.1
ii libsystemd0 241-7~deb10u1
ii libtinfo6 6.1+20181013-2+deb10u1
ii libudev1 241-7~deb10u1
ii libuuid1 2.33.1-0.1
ii login 1:4.5-1.1
ii zlib1g 1:1.2.11.dfsg-1
util-linux recommends no packages.
Versions of packages util-linux suggests:
pn dosfstools <none>
ii kbd 2.0.4-4
pn util-linux-locales <none>
-- debconf information:
util-linux/noauto-with-nonzero-passnum:
